Leiomyosarcoma of the Inferior Vena Cava: Capitalizing and Harnessing the Real-time Imaging and Online Adaptive Radiotherapy by Magnetic Resonance Imaging-guided Linear Accelerator

A BSTRACT Primary treatment for soft tissue leiomyosarcoma (LMS) is surgical excision; however, its frequent recurrence necessitates the options such as chemotherapy, radiation, and advancements like MR-guided radiation therapy (MRgRT) improves treatment outcomes. A 59-year old postmenopausal female presented with complaints of lower abdominal pain and lower backache for the past 6 months. A positron emission tomography and computed tomography (PET CT) whole body revealed an enlarged right paracaval lymph node. Laparoscopic excision was carried out. Intraoperatively, the mass was noted in the retrocaval region, adherent and arising from the posterior wall of the inferior vena cava (IVC). Histopathological examination revealed a malignant spindle cell tumor likely LMS. While immunohistochemistry showed positive for H-caldesmon and smooth muscle actin and negative for estrogen receptor. Postoperative magnetic resonance imaging (MRI) revealed focal, irregular soft tissue along the posterior wall of the IVC. She was planned for adjuvant radiation using MRgRT, and generated plan of the day was delivered under continuous real-time MRI of the target. On 3-monthly follow-up, PET CT scan revealed complete resolution of metabolic activity and a significant decrease in the size of the lesion.